18. Medindo a distância e velocidade do som com saída no monitor

Usamos o HC-SR04 Ultrasonic Distance Measuring Sensor Module para medir distâncias e imprimi-las no monitor.  Veja a Aula 17 deste curso: http://www.toptechboy.com/arduino-lessons/

int trigPin=13; //Sensor Trip pin connected to Arduino pin 13
int echoPin=11;  //Sensor Echo pin connected to Arduino pin 11
float pingTime;
float targetDistance;
int speed= 345; //sound speed in m/s at 26C at see level
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
void loop() {
  // put your main code here, to run repeatedly: 
  
  digitalWrite(trigPin, LOW); //Set trigger pin low
  delayMicroseconds(2000); //Let signal settle
  digitalWrite(trigPin, HIGH); //Set trigPin high
  delayMicroseconds(10); //Delay in high state
  digitalWrite(trigPin, LOW); //ping has now been sent
  
  pingTime = pulseIn(echoPin, HIGH);  //pingTime is presented in microceconds

  targetDistance = speed*pingTime/1000000/2; 
  Serial.print("the distance is: ");
  Serial.print(targetDistance);
 Serial.println("    m");
  delay(1000);
}

Para medir a velocidade do som, partimos de uma distância bem determinada (digamos, 20cm) e modificamos o código acima do seguinte modo: 

int trigPin=13; //Sensor Trip pin connected to Arduino pin 13
int echoPin=11;  //Sensor Echo pin connected to Arduino pin 11
float pingTime;
float speedOfSound;
float targetDistance=0.2; //Distance to Target in m
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
void loop() {
  // put your main code here, to run repeatedly: 
  
  digitalWrite(trigPin, LOW); //Set trigger pin low
  delayMicroseconds(2000); //Let signal settle
  digitalWrite(trigPin, HIGH); //Set trigPin high
  delayMicroseconds(10); //Delay in high state
  digitalWrite(trigPin, LOW); //ping has now been sent
  
  pingTime = pulseIn(echoPin, HIGH);  //pingTime is presented in microceconds

  speedOfSound = (targetDistance*2)/pingTime*1000000; 
  Serial.print("The Speed of Sound is: ");
  Serial.print(speedOfSound);
 Serial.println("    m/s");
  delay(1000);

}